1. Field of the Invention
The present invention relates to a head-mounted display apparatus arranged to be mountable on the head of a user to enable the user to observe a video image.
2. Description of Related Art
Visual display apparatuses called the head-mounted display apparatus arranged to enable the user to see a video image, or an image from a personal computer, on the image plane of a display device mounted on the head of the user have been disclosed, for example, in Japanese Laid-Open Patent Applications No. HEI 7-84210, No. HEI 7-181422, No. HEI 7-333547, etc.
With a head-mounted display apparatus mounted on the head of the user, the user can satisfactorily enjoy viewing video images or the like at any place without disturbing surroundings. The head-mounted display apparatus, therefore, must be easy to mount, light in weight, readily mountable and demountable and excel in portability. The known head-mounted display apparatuses are briefly described as follows.
(1) A head-mounted display apparatus disclosed in Japanese Laid-Open Patent Application No. HEI 7-84210 is in a shape having the rear portion of its mount part cut away. The head-mounted display apparatus is arranged to be mounted from the front of the head of the user in a readily demountable manner, giving the user a jaunty feeling of mounting the head-mounted display apparatus without touching the rear part of the head, and lightly pressing the head with a pressing holding member which is made of an elastic material such as metal or plastic.
(2) A head-mounted display apparatus disclosed in Japanese Laid-Open Patent Application No. HEI 7-181422 has its mount part formed to encompass the head of the user. The head-mounted display apparatus is arranged to be secured to the head of the user with the mount part being urged toward the two sides of the head of the user.
(3) A video image display apparatus disclosed in Japanese Laid-Open Patent Application No. HEI 7-333547 has a display part mounted on a mount frame. The mount frame is provided with a movable frame. The video image display apparatus is arranged to be fixed to the head of the user by urging the movable frame toward the head.
(4) In a head-mounted display apparatus of the head encompassing type, which has been marketed during recent years, an earphone-cable stowing mechanism which is disposed inside of the mount part is provided for the purpose of passing earphone cables through the inside of the mount part.
(5) In another head-mounted display apparatus, which has also been recently marketed, temples extending from a nose-touching part like spectacles are provided, and earphones are stowable at the fore ends of the temples.
However, the above conventional head-mounted display apparatuses have problems, as described below, and the solution of the problems has been desired.
The head-mounted display apparatus mentioned in the above Para. (1) can be easily mounted without any disagreeable feeling in the rear part of the head of the user. However, the pressing holding member is provided with an adjusting mechanism for adjustment of a pressing force. This adjusting mechanism increases the weight of the apparatus to degrade the light feeling of mounting. Further, the partly-cutaway head-encompassing shape of the frame causes the size of the apparatus to increase. The increased size of the apparatus degrades its portability, which is important for enabling the user to enjoy viewing a video image at any desired places.
The apparatus is secured to the head by pressing the head with the pressing holding member, which is made of an elastic material such as metal, plastic or the like. In a case where a plastic or the like is used, the pressing holding member is caused to creep to loosen by the continuous use over a long period of time and comes to necessitate adjustment of its elastic force. However, it tends to eventually become impossible to obtain a necessary elastic force by adjustment. In a case where a metal material is used as the elastic material, when the pressing holding member is spread for mounting the apparatus on the head, lack of design consideration as to properties and sectional shape of the material tends to incur a permanent set of fatigue with its internal stress coming to exceed the limit of elasticity. The use of a metal material thus also necessitates the adjustment of the elastic force, which might eventually become impossible.
In the case of the head-mounted display apparatus mentioned in the above Para. (2), a display part is fixed to the head of the user with a headband-like mount part. It takes time to correctly mount the display part with the mount part. The display part is relatively heavy and requires use of a relatively strong force in fixing the display part to the head of the user. The use of the relatively strong force not only causes the user to feel some pressure but also leaves some trace of mounting to the hair of the head of the user.
The video image display apparatus mentioned in the above Para. (3) is easily mountable as it is arranged to be mounted from the front of the face of the user and does not give any local pushed feeling as it does not press the head over the whole circumference thereof. However, the movable frame is arranged to be urged toward the head. A reaction to this urging force is received by the mount frame. The mount frame, therefore, must be arranged to have a sufficient rigidity against the reaction. As a result, the weight of the apparatus increases to impair the feeling of having the apparatus mounted on the head of the user.
The head-mounted display apparatus mentioned in the above Para. (4) has the earphone cables passed through the inside of its mount part. The mount part must have a larger thickness for this purpose. Besides, the earphone-cable stowing mechanism provided for the earphone cables also increases the weight of the apparatus. The arrangement is impedimental both to a jaunty appearance and to reduction in actual weight.
The head-mounted display apparatus mentioned in the above Para. (5) is arranged to have the weight of the apparatus received by the nose of the user, which is sensitive. Therefore, the use of the apparatus over a long period of time gives a disagreeable feeling to the user. Another problem with the apparatus lies in that, while earphones are provided with ear pads in general, the apparatus is arranged such that, in stowing the earphone at the fore end part of the temple, the peripheral portion of a part of the earphone to be inserted into the ear is inserted into the fore end stowing part of the temple. The arrangement, therefore, tends to damage the ear pads.